Constant pressure variable displacement pump



March 22, 1960 DE Loss D. WALLACE 2,929,329

CONSTANT PRESSURE VARIABLE DISPLACEMENT PUMP Filed nec. e, 195s Fig. 2

INVENTOR. DeLoss D, Wal/ace BY Q Jr H/'s Attorney United States Patent() CONSTANT PRESSURE VARIABLE DISPLACEMENT PUMP DeiLoss D. Wallace, Dayton, Ohio, assignor to General Motors Corporation, Detroit, Mich., a corporation of Delaware Application December 6, 1956, Serial No. 626,731 7 Claims. (Cl. 10S-120) This invention relates to a pump and more particularly to a constant pressure variable displacement pump wherein the displacement of the pump is automatically'controlledby the shifting of a control slide that enclrcles a rotary pump impeller.

The present day constant pressure variable displacement pump makes use of high pressure outlet liuid for radially shifting the control ring of the pump relative to the pump impeller. In such a structure shifting of the control ring or control slide is in response to high pressure changes at the outlet side of the pump which are in turn brought about by changing quantity demand on the pump. The high pressure control uid in these pumps is opposed by compression springs that normally move the control slide to the maximum displacement position. Where high pressure is used as the control force and where such pressure is applied to a relatively large pressure area on the control slide it is obviousthat very heavy compression springs must also be used. In some instances this has brought about a sluggish control of the pump and a slow displacement varying response due to the fact that a great change in pressure is needed to shift the control ring where high pressure :duid is used as the controlling force. It is an object of this invention to provide a constant pressure variable displacement pump wherein the shifting of the control slide of the pump is brought about by the application of high pressure uid acting on a relatively small pressure area and where relatively light compression springs may be used in opposing the force set up by the high pressure iluid.

The pump according to this invention has a pair of oppositely disposed pressure chambers that act on opposite endsv of the control slide of the pump to hold the control slide in substantial balance in the direction of movement of the control slide. With this arrangement high pressure uid is applied to a relatively small pressure area on the control slide and the force set up by the'lpressure acting on this area is opposed bylight compression springs. This structure exhibits accurate control characteristics and is highly responsive to changes in outlet pressure of the pump.

Another object of this invention is to provide a constant pressure variable displacement pump wherein the forces acting on the control slide of the pump in a direction normal to the direction of movement of the control slide are substantially balanced to reduce lateral thrust on the control slide.

Further objects and advantages of the present invention will be apparent from the following description, referencebeinghad to the accompanying drawings, wherein a preferred form of the present invention is clearly shown.

In the drawings:

Figure 1 is avertical sectional view with parts broken away of a pump made in accordance with this invention;

n .springs 46. In other words the distance between liange tending vanes 52.

Figure 2 is a sectional view taken along lines 2-2 of Figure 1. y

Referring now to the drawings the pump of this invention s generally designated by reference numeral 10 and comprises a generally cylindrical casing 12 interposed between a pair of end plates 14 and 16. The cylindrical casing 12 and the end plates 14 and 16 are held together by a plurality of bolts 18. A rotor shaft 20 is journaled in suitable bearings formed in the end plates 14 and 16 and is held from axial movement by a C-shaped snap ring 22. The end of lshaft 20 is covered by an end cap 24 that is bolted to the end plate 16.

'I'he generally cylindrically shaped casing 12 is provided with a low pressure inlet chamber 26 that is connected with a low pressure inlet passage 28 and with a high pressure outlet chamber 30 connected with an outlet passage 32. The casing 12 is further provided with a lower chamber 34 and with an upper second chamber 36. A control slide generally denoted by reference numeral 38 is supported within the casing 12 and has a lower portion 39 slidably engaging ange portions 40 on casing 12. The upper part 42 of the control slide 38 slidably engages the walls 44 of the chamber 36. A pair of relatively light compression springs 46 are interposed between the lower portion 39 of the slide 38 and the easing 12.

The impeller shaft 20 of the pump carries a pump rotor 48 that is keyed to the shaft for rotation therewith. The pump rotor 48 has a plurality of radially extenting slots 50 that carry a plurality of radially ex- The vanes 52 are radially slidable Within the slots 50 and are engaged at their inner ends by a priming ring 54. The priming ring 54 floats in an axially grooved portion of the pump rotor 48 as more particularly shown in Figure 2. The vanes 52 are thus held between the interior wall of control slide 38 and Y within the pumping rotor 48 holds the vanes 52 tightly' against the bore of the control slide.

The control slide 38 is provided with passages 56 which connect the low pressure chamber 26 with the interior of the control slide and with passages 58 that connect the high pressure chamber 30 with the interior of the control slide. With this arrangement fluid pressure entering chamber 26 ows through the passages 56 and is moved by the vanes 52 to the outlet passages 58. The pumping rate of the pump depends on the excentricity of the control slide 38 with respect to the pumping rotor 48. When the control slide 38 is concentric with the pumping rotor 48 the output of the pump is substantially zero. As the control slide 38 is shifted upwardly in Figure l the displacement of the pump is increased when the shaft 2.0 is rotating in a counter clockwise direction.

The radial movement of control slide 38 along a vertical axis in Figure 2 is controlled by applying Various iiuid pressures to opposite ends of the control slide.v

u pressure` area of the lower end of the slide that is lovcated parallel to end face 64. The lower end area -includes the lower face ofrend cap 66, the area that abuts the top ends of springs 46 generally denoted by reference numeral 68 and the end areas 70 adjacent the The lower portion of the control slide Ya8v is :provided with a chamber generally denoted by reference -numeral 72 and closed by the end cap 66. A iixed piston 74 is se-A cured to end plates 14 and 16 and is disposed within the chamber 72 and divides the chamber into pressure chambers 76 and 78. The chamber 76 is connected with the low pressure inlet by the passage 6 2 and pressure in this chamber operates on a pressure area 80 formed on the control slide 38 and located normal tothe direction of movement of the control slide. The chamber 78 connected with the high pressure outlet chamber 30 by passages 82, 84 and 86. These passages are drilled into the end wall 16, High pressure fluid in chamber 78 operates on a pressure area 88 located normal to the direction of movement of the control slide and being of the same area as presusre area 80. l

ln operation the shaft 20 is rotated in a counter clockwise direction thereby rotating the vanes 52 and moving uid from the inlet 2S to the outlet 32. The inlet pressure is present within the chamber 36 and within the chamber 34 and acts on the upper end face 64 of the control siide 38 and on the lower end face of thercontrol slide 38. Since the eiiective pressure areas of the upper and lower ends of the control slide are equal the forces' produced by the low pressure iiuid in chamber 36 and in chamber 3dare opposite and equal. The springs 46 and the low pressure in chamber 76 however, operate to move the control slide 38 upwardly toward the maximum'displacement position of the pump. The forces produced by the pressure in chamber 76 and by the control spring 46 is variably opposed by high pressure liuid in chamber 78 which operates to move the control slide toward a reduced pump displacement position. The control slide 38 is thus substantially in force balance in the' direction of movement of the control slide due tok the fact thatA the pressure in chamber 78 offsets thepressure in chamber '76 when the pump first builds up to pressure and thereafter the control is brought about by uotuations in the outlet pressure in chamber 78. AsA the outlet pressure increases the slide 38 is moved downwardly to decrease the displacement of the pump and is moved upwardly to increase the displacement of the pump upon reduction of outlet pressure. Since the presure area 88 is substantially smaller than the end areas of thevcontrol slide 38 a very simple and' highly responsive control for shifting the control slide is provided. Moreover the control springs 46 may be relatively light since the high pressure is acting on an area that is considerably smaller than the end face 64 of the slide 38.

It should also be noted that the control slide 38 is balanced in a direction normal to the direction of movement of `the control slide. This balance is due to the fact that low pressure is acting on opposite sides ofthe right hand portion 9G of the control slide 38 while high pressure is acting on opposite sides of the left hand portion 92 of the control slide. The portions 90l and 92 are arcuately shaped and have the same effective pressure areas on the inside and on the outside thereof. By providing a substantial balance in all directions for the control slide 38 the ilange portions 40 and 44 may be reduced in length and will still provide effective support for the slide 38.

While the form of embodiment of theinvention as herein disclosed constitutes a preferred form, it is to be understood that other forms might be adopted, als` may come within the scope or the claims which follow.

What is claimed is as follows: Y

l. A constant pressure variable displacement pump' ins-,said casingisupported for straight-line'radial move-"75 2,929,329 y s s ment within said casing, said control member being hollow to 'form a pump chamber, a pump impeller in 'said chamber carrying a plurality of peripherally extending vanes, a low pressure inlet and a high pressure outlet communicating with said pump chamber, a pair of oppositely disposed balancing chambers defined by a pair of control member end walls and said casing, the eiective pressure areas of said end Walls being equal, passage means connecting said balancing chambers with the same pressure of said pump, a compression spring interposed between said casing and said control member for biasing said control member in a direction t'o increasenthe placement of said pump, a iiuid motor Within said cntrol member operable when supplied with pressure uid for forcing said control member in an opposite direction, and passage means connecting one side ohly of said ud motor with the high pressure outlet of said pump.

2. A constant pressure variable displacement pump comprising, a hollow casing, a pumpir'n'peller including a plurality of peripherally extending varies in said casing, a pump control member encircling said impeller and forming therewith a pump chamber and radially movable* along a `straight line relative to said impellerfor varying the displacement of said pump, a low pressure inlet and a high pressure outlet for said pump communicating. with the interior of said control member, a pair of oppositely disposed balancing chambers defined by opposite yend 'walls of said control member and said casing, the effet: tive pressureareas of said end walls being equal, pas# sage means connecting the same pressure withIk said balancing chambers, whereby said control memberis sub:- jected to equal and opposite forces in a radial direction; a compression spring opcrably connected with said control member biasing said control memberA in said radial direc-" tion to increase the displacement of said pump, afiiuid motor within said control member having a chamber oir each of opposite sides of a stationary piston walla'nd operable to move said control member in an oppositeu direction when fluid pressure is supplied to one of said' chambers, and passage means connecting said pump high pressure outlet and said one chamber.

3. A constant pressure variable displacement pump' comprising, a casing having a generally cylindricallyA- shaped chamber, a rotary pump impeller in said chamber having a plurality of peripherally extending van'es.,l a hollow control slide encircling said impeller forming a1 pump chamber and including a pair of side walls spaced from said casing and forming therewith alow pressure in-f' let chamber and a high pressure outlet chamber, said control slide being supported by said casing for radial straight-line movement and having a pair of end wallsmovable within recessed portions of said casing and forming balancing chambers therewith, passage means' connecting the interior of said slideV with said inlet charn4 ber and connecting the interior of said slide with said' outlet chamber, said side walls have interior and external: areas' of equal size whereby the forceson said slideare substantially opposite and equal in a direction substani tally normal to said radial direction, passage means con-mnecting-saidlbalancing chambers with said lowv pressure' inlet, the eiective pressure areas of said end walls being equal'whereby the forces on said control slide due to pressurizing of said balancing chambers witlilow pressure fluid are opposite and equal in said radial direction,l av

compression spring biasingV said' control Aslide i'riusaid radial direction and in a direction to increase lthe Vtlisplacement of said pump, a fluid chamber in saidslide, an stationary piston in said duid chamber, saidpiston and chamber forming an actuating 4, A. .constant pressure variable displacement chamber@Y receiving uidY pressure to force said slide in said radial direction vtox comprising, a hollow casing, a low pressure inlet and a high pressure outlet in said casing, a rotary pump impeller in said casing having peripherally extending vanes, a control slide encircing said impeller and slidably supported in said casing for radial straight-line movement, the opposite ends of said control slide defining with said casing a pair of oppositely disposed balancing chambers, said opposite ends having equal eiiective pressure areas, passage means connecting said balancing chambers with said low pressure inlet whereby said slide is subjected to equal and opposite forces by low pressure luid in said balancing chambers in a radial direction, a compression spring biasing said slide in said radial direction to increase the displacement of said pump, said slide having a pair of oppositely disposed pressure areas located normal to the direction of movement of said slide, means including said pressure areas dening iiuid pressure chambers and passage means connecting one of said pressure chambers with said low pressure inlet and connecting the other of said pressure chambers with said high pressure outlet, the low pressure duid in said one chamber operating on the pressure area associated therewith to move said slide in a direction increasing the displacement of said pump, the high pressure iiuid in the other of said charnbers operating on the pressure area associated therewith to move said slide in a direction decreasing the displacement of said pump.

5. A constant pressure variable displacement pump comprising, a hollow casing, a low pressure inlet and a high pressure outlet in said casing, a rotary impeller having a plurality of peripherally extending vanes in said casing, a control member having a portion encircling said impeller and slidably supported in said casing, said control member being radially movable relative to said impeller for varying the displacement of said pump, a pair of oppositely disposed balancing chambers defined by oppositely disposed end faces of said control slide and said casing, passage means connecting said balancing chambers with said low pressure inlet, said end faces having equal effective pressure areas whereby low pressure fluid entering said balancing chambers subjects said slide to equal and opposite forces, a compression spring interposed between control member and said casing biasing said control member in a radial direction to increase the displacement of' said pump, a pressure chamber in said control member having equal oppositely disposed pressure areas located normal to the radial direction of movement of said control member, a piston fixed to said casing in said pressure chamber intermediate said pressure areas dividing said pressure chamber into iirst and second actuating chambers, and passage means connecting said first actuating chamber with said low pressure inlet and connecting said second actuating chamber with said high pressure outlet, the low pressure fluid in said first chamber operating on the pressure area associated with said rst chamber to move said control member in a direction increasing the displacement of said pump, the high pressure in said second chamber operating on the pressure area associated with said second chamber to move said control member in a direction to decrease the displacement of said pump.

6. The structure defined in claim 5 wherein said control member includes a pair of oppositely disposed side walls joining said end faces and located respectively adjacent said inlet and outlet, the side Walls each having a passage connecting said inlet and outlet With the interior of the control member, each side wall having equal eective pressure areas on either side thereof whereby the control member is subject to equai and opposite forces in a direction normal to the radial displacement varying movement of said control member.

7. A constant pressure variable displacement pump comprising, a hollow casing, a low pressure inlet and a high pressure outlet associated with said casing, a rotary pump impeller having a plurality of peripherally extending vanes in said casing, a control slide supported by said casing having a portion encircling said impeller and radially movable for varying the displacement of saidl pump, a pair of oppositely disposed pressure areas on said control slide located substantially normal to the displacement varying direction of movement of said slide and having equal effective balancing areas, a third pressure area on said slide located parallel to said balancing pressure areas but of substantially smaller area than either of said balancing areas, means for applying low pressure inlet fluid from said low pressure inlet against all of said areas, said low pressure inlet duid producing equal and opposite forces on said slide by reason of said balancing arcas and producing a smaller control force in a direction increasing the displacement of said pump by reason of said third pressure area, a fourth pressure area on said slide located parallel to said balancing areas but substantially smaller in area than either of said balancing areas, and means applying high pressure outlet fluid to said fourth area from said high pressure outlet, said high pressure outlet fluid producing a control force on said slide in a direction to decrease the displacement of said pump and in opposition to the force produced by said low pressure inlet uid acting on said third pressure area.

References Cited in the le of this patent UNITED STATES PATENTS 1,370,810 Hansen Mar. 8, 1921 1,779,757 Streckert Oct. 28, 1930 1,943,929 Rayburn Jan. 16, 1934 2,031,749 Vincent Feb. 25, 1936 2,080,810 Douglas May 18, 1937 2,296,876 Samiran et al Sept. 29, 1942 2,612,114 Ernst Sept. 30, 1952 2,678,607 Hulerd et al. May 18, 1954 

